A study of four fish farms on the west coast of Scotland between 1990 and 1992 (Bron et al. 1993) found that fallowing was effective in controlling lice numbers on Atlantic salmon. The salmon at site 1 were heavily infected with lice throughout the period of the study and therefore required regular treatment. Lice numbers were low in new smolts at sites 2-4 (where fallowing took place) and treatment wasn’t required as often as for site 1 (where there was no fallowing). Treatment for lice wasn’t required as often for salmon at sites 2 and 3 (long fallow periods of at least 16 weeks) compared to site 4 (fallow period of around 9 weeks) suggesting longer periods of fallowing were more effective in controlling lice numbers. The four farms had fallowing periods of 0, 17, 16 and 9 weeks respectively (hereby sites 1, 2, 3 and 4 respectively). Sites 2-4 contained only one intake of salmon at a time whereas site 1 contained salmon of multiple year classes. Samples of salmon were taken from each farm every two weeks for 20 months and lice numbers (of species L.salmonis and C.elongatus) were counted.